Nostoc
Explanation:
Oedogonium, Chlorella, and Volvox are not blue-green algae. They are green algae, which are a different group of photosynthetic organisms.
Nostoc is a genus of blue-green algae that are known for their nitrogen-fixing abilities. Nitrogen fixation is the process of converting atmospheric nitrogen into ammonia, which can then be used by plants for growth.
